1. Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences Fukuoka 812‐8582 Japan
2. Department of Microbiology, Asahikawa Medical College, Midorigaoka‐Higashi Asahikawa 078‐8510 Japan
3. Department of Molecular Microbiology, Research Institute for Microbial Diseases, Osaka University Suita 565‐0871 Japan